1. Field of the Invention
This invention relates to apparatus which utilizes the rotary motion imparted to a member as the motive force for a pump.
2. Description of the Prior Art
It is well-known in the art that the magnitude of the pressure differential across a seal between a stationary and a relatively rotatable member increases the forces imposed on the seal and commensurately reduces the operating life thereof. This is especially true in the hydrocarbon drilling environment where seals are typically used on various downhole tools.
U.S. Pat. No. 3,600,109 (Pavlichenko, et al.) relates to an arrangement to seal the shaft of a drilling face machine. U.S. Pat. No. 3,894,818 (Tschirky) relates to an in-hole motor in which thrust bearings are provided with means to lubricate the bearings employing pressure balanced seals.
Other sealing arrangements between a relatively rotating shaft and a stationary housing are those disclosed in U.S. Pat. No. 3,740,057 (Doyle, et al.), U.S. Pat. No. 3,888,495 (Mayer) and U.S. Pat. No. 4,080,115 (Sims, et al.).
U.S. Pat. No. 4,039,229, issued to Ohlberg discloses a roller bearing construction which includes at least one bounding wall fabricated of an elastic material. U.S. Pat. No. 1,892,217, issued to Moineau discloses a gear mechanism adapted for use as a pump, a prime mover or a fluid transmission means.
Until very recently, some downhole tools, more particularly turbodrills, have been used to drill oil wells with thrust bearings constructed from laminations of rubber and steel. Lubrication and cooling were provided by the drilling mud circulating in the well bore. Their poor performance in such environment compelled designers, engineers and operators to shift to standard bearings (balls, rollers, etc.) operating in a clean lubricant. This required sealing off the chamber housing the bearings system from any intrusion of contaminants present in the drilling mud and the mud itself.
The duration of efficient operation depends on the life of the bearings, among other factors, and in turn the life of the bearings depends on the life of the seals separating the clean lubricant from the drilling mud.
A significant factor controlling the life of these seals is the differential pressure across them. Reducing the pressure differential across these seals using a modified roller bearing as prime mover for a pump is considered to be a feature of the present invention.
It would be advantageous to utilize the rotary motion necessarily imparted to a downhole tool as the motive force for a pump. Further, it is believed to be advantageous to provide a seal arrangement for use in the hydrocarbon production environment wherein the motive force generated by the rotation of the shaft is imparted to a bearing member and is utilized to pump lubricating fluid between internal chambers to thereby equalize pressure differences across the shaft sealing members. Also believed advantageous as a consequence of the pumping of lubricating fluid between internally defined chambers is the circulation of the lubricating fluid so that a heat transfer relationship between the fluid and the structural members may be provided to lower bearing operating temperatures. It is also advantageous to generate the higher pressures of the fluid on the "inside" of the seals to insure that any leakage flow tends to be in a direction from the inside to the outside, thus effectively isolating the region between the seals from the region outside the seals.